1 /*
2 * Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
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24 */
25
26 /*
27 * This file is available under and governed by the GNU General Public
28 * License version 2 only, as published by the Free Software Foundation.
29 * However, the following notice accompanied the original version of this
30 * file:
31 *
32 * Copyright (c) 2007-2012, Stephen Colebourne & Michael Nascimento Santos
33 *
34 * All rights reserved.
35 *
36 * Redistribution and use in source and binary forms, with or without
37 * modification, are permitted provided that the following conditions are met:
38 *
39 * * Redistributions of source code must retain the above copyright notice,
40 * this list of conditions and the following disclaimer.
41 *
42 * * Redistributions in binary form must reproduce the above copyright notice,
43 * this list of conditions and the following disclaimer in the documentation
44 * and/or other materials provided with the distribution.
45 *
46 * * Neither the name of JSR-310 nor the names of its contributors
47 * may be used to endorse or promote products derived from this software
48 * without specific prior written permission.
49 *
50 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
51 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
52 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
53 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
54 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
55 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
56 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
57 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
58 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
59 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
60 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
61 */
62 package java.time;
63
64 import static java.time.LocalTime.MINUTES_PER_HOUR;
65 import static java.time.LocalTime.SECONDS_PER_HOUR;
66 import static java.time.LocalTime.SECONDS_PER_MINUTE;
67 import static java.time.temporal.ChronoField.OFFSET_SECONDS;
68
69 import java.io.DataInput;
70 import java.io.DataOutput;
71 import java.io.IOException;
72 import java.io.InvalidObjectException;
73 import java.io.ObjectInputStream;
74 import java.io.Serializable;
75 import java.time.temporal.ChronoField;
76 import java.time.temporal.Temporal;
77 import java.time.temporal.TemporalAccessor;
78 import java.time.temporal.TemporalAdjuster;
79 import java.time.temporal.TemporalField;
80 import java.time.temporal.TemporalQueries;
81 import java.time.temporal.TemporalQuery;
82 import java.time.temporal.UnsupportedTemporalTypeException;
83 import java.time.temporal.ValueRange;
84 import java.time.zone.ZoneRules;
85 import java.util.Objects;
86 import java.util.concurrent.ConcurrentHashMap;
87 import java.util.concurrent.ConcurrentMap;
88
89 /**
90 * A time-zone offset from Greenwich/UTC, such as {@code +02:00}.
91 * <p>
92 * A time-zone offset is the amount of time that a time-zone differs from Greenwich/UTC.
93 * This is usually a fixed number of hours and minutes.
94 * <p>
95 * Different parts of the world have different time-zone offsets.
96 * The rules for how offsets vary by place and time of year are captured in the
97 * {@link ZoneId} class.
98 * <p>
99 * For example, Paris is one hour ahead of Greenwich/UTC in winter and two hours
100 * ahead in summer. The {@code ZoneId} instance for Paris will reference two
101 * {@code ZoneOffset} instances - a {@code +01:00} instance for winter,
102 * and a {@code +02:00} instance for summer.
103 * <p>
104 * In 2008, time-zone offsets around the world extended from -12:00 to +14:00.
105 * To prevent any problems with that range being extended, yet still provide
106 * validation, the range of offsets is restricted to -18:00 to 18:00 inclusive.
107 * <p>
108 * This class is designed for use with the ISO calendar system.
109 * The fields of hours, minutes and seconds make assumptions that are valid for the
110 * standard ISO definitions of those fields. This class may be used with other
111 * calendar systems providing the definition of the time fields matches those
112 * of the ISO calendar system.
113 * <p>
114 * Instances of {@code ZoneOffset} must be compared using {@link #equals}.
115 * Implementations may choose to cache certain common offsets, however
116 * applications must not rely on such caching.
117 *
118 * <p>
119 * This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>
120 * class; use of identity-sensitive operations (including reference equality
121 * ({@code ==}), identity hash code, or synchronization) on instances of
122 * {@code ZoneOffset} may have unpredictable results and should be avoided.
123 * The {@code equals} method should be used for comparisons.
124 *
125 * @implSpec
126 * This class is immutable and thread-safe.
127 *
128 * @since 1.8
129 */
130 public final class ZoneOffset
131 extends ZoneId
132 implements TemporalAccessor, TemporalAdjuster, Comparable<ZoneOffset>, Serializable {
133
134 /** Cache of time-zone offset by offset in seconds. */
135 private static final ConcurrentMap<Integer, ZoneOffset> SECONDS_CACHE = new ConcurrentHashMap<>(16, 0.75f, 4);
136 /** Cache of time-zone offset by ID. */
137 private static final ConcurrentMap<String, ZoneOffset> ID_CACHE = new ConcurrentHashMap<>(16, 0.75f, 4);
138
139 /**
140 * The abs maximum seconds.
141 */
142 private static final int MAX_SECONDS = 18 * SECONDS_PER_HOUR;
143 /**
144 * Serialization version.
145 */
146 private static final long serialVersionUID = 2357656521762053153L;
147
148 /**
149 * The time-zone offset for UTC, with an ID of 'Z'.
150 */
151 public static final ZoneOffset UTC = ZoneOffset.ofTotalSeconds(0);
152 /**
153 * Constant for the minimum supported offset.
154 */
155 public static final ZoneOffset MIN = ZoneOffset.ofTotalSeconds(-MAX_SECONDS);
156 /**
157 * Constant for the maximum supported offset.
158 */
159 public static final ZoneOffset MAX = ZoneOffset.ofTotalSeconds(MAX_SECONDS);
160
161 /**
162 * The total offset in seconds.
163 */
164 private final int totalSeconds;
165 /**
166 * The string form of the time-zone offset.
167 */
168 private final transient String id;
169
170 //-----------------------------------------------------------------------
171 /**
172 * Obtains an instance of {@code ZoneOffset} using the ID.
173 * <p>
174 * This method parses the string ID of a {@code ZoneOffset} to
175 * return an instance. The parsing accepts all the formats generated by
176 * {@link #getId()}, plus some additional formats:
177 * <ul>
178 * <li>{@code Z} - for UTC
179 * <li>{@code +h}
180 * <li>{@code +hh}
181 * <li>{@code +hh:mm}
182 * <li>{@code -hh:mm}
183 * <li>{@code +hhmm}
184 * <li>{@code -hhmm}
185 * <li>{@code +hh:mm:ss}
186 * <li>{@code -hh:mm:ss}
187 * <li>{@code +hhmmss}
188 * <li>{@code -hhmmss}
189 * </ul>
190 * Note that ± means either the plus or minus symbol.
191 * <p>
192 * The ID of the returned offset will be normalized to one of the formats
193 * described by {@link #getId()}.
194 * <p>
195 * The maximum supported range is from +18:00 to -18:00 inclusive.
196 *
197 * @param offsetId the offset ID, not null
198 * @return the zone-offset, not null
199 * @throws DateTimeException if the offset ID is invalid
200 */
201 @SuppressWarnings("fallthrough")
202 public static ZoneOffset of(String offsetId) {
203 Objects.requireNonNull(offsetId, "offsetId");
204 // "Z" is always in the cache
205 ZoneOffset offset = ID_CACHE.get(offsetId);
206 if (offset != null) {
207 return offset;
208 }
209
210 // parse - +h, +hh, +hhmm, +hh:mm, +hhmmss, +hh:mm:ss
211 final int hours, minutes, seconds;
212 switch (offsetId.length()) {
213 case 2:
214 offsetId = offsetId.charAt(0) + "0" + offsetId.charAt(1); // fallthru
215 case 3:
216 hours = parseNumber(offsetId, 1, false);
217 minutes = 0;
218 seconds = 0;
219 break;
220 case 5:
221 hours = parseNumber(offsetId, 1, false);
222 minutes = parseNumber(offsetId, 3, false);
223 seconds = 0;
224 break;
225 case 6:
226 hours = parseNumber(offsetId, 1, false);
227 minutes = parseNumber(offsetId, 4, true);
228 seconds = 0;
229 break;
230 case 7:
231 hours = parseNumber(offsetId, 1, false);
232 minutes = parseNumber(offsetId, 3, false);
233 seconds = parseNumber(offsetId, 5, false);
234 break;
235 case 9:
236 hours = parseNumber(offsetId, 1, false);
237 minutes = parseNumber(offsetId, 4, true);
238 seconds = parseNumber(offsetId, 7, true);
239 break;
240 default:
241 throw new DateTimeException("Invalid ID for ZoneOffset, invalid format: " + offsetId);
242 }
243 char first = offsetId.charAt(0);
244 if (first != '+' && first != '-') {
245 throw new DateTimeException("Invalid ID for ZoneOffset, plus/minus not found when expected: " + offsetId);
246 }
247 if (first == '-') {
248 return ofHoursMinutesSeconds(-hours, -minutes, -seconds);
249 } else {
250 return ofHoursMinutesSeconds(hours, minutes, seconds);
251 }
252 }
253
254 /**
255 * Parse a two digit zero-prefixed number.
256 *
257 * @param offsetId the offset ID, not null
258 * @param pos the position to parse, valid
259 * @param precededByColon should this number be prefixed by a precededByColon
260 * @return the parsed number, from 0 to 99
261 */
262 private static int parseNumber(CharSequence offsetId, int pos, boolean precededByColon) {
263 if (precededByColon && offsetId.charAt(pos - 1) != ':') {
264 throw new DateTimeException("Invalid ID for ZoneOffset, colon not found when expected: " + offsetId);
265 }
266 char ch1 = offsetId.charAt(pos);
267 char ch2 = offsetId.charAt(pos + 1);
268 if (ch1 < '0' || ch1 > '9' || ch2 < '0' || ch2 > '9') {
269 throw new DateTimeException("Invalid ID for ZoneOffset, non numeric characters found: " + offsetId);
270 }
271 return (ch1 - 48) * 10 + (ch2 - 48);
272 }
273
274 //-----------------------------------------------------------------------
275 /**
276 * Obtains an instance of {@code ZoneOffset} using an offset in hours.
277 *
278 * @param hours the time-zone offset in hours, from -18 to +18
279 * @return the zone-offset, not null
280 * @throws DateTimeException if the offset is not in the required range
281 */
282 public static ZoneOffset ofHours(int hours) {
283 return ofHoursMinutesSeconds(hours, 0, 0);
284 }
285
286 /**
287 * Obtains an instance of {@code ZoneOffset} using an offset in
288 * hours and minutes.
289 * <p>
290 * The sign of the hours and minutes components must match.
291 * Thus, if the hours is negative, the minutes must be negative or zero.
292 * If the hours is zero, the minutes may be positive, negative or zero.
293 *
294 * @param hours the time-zone offset in hours, from -18 to +18
295 * @param minutes the time-zone offset in minutes, from 0 to ±59, sign matches hours
296 * @return the zone-offset, not null
297 * @throws DateTimeException if the offset is not in the required range
298 */
299 public static ZoneOffset ofHoursMinutes(int hours, int minutes) {
300 return ofHoursMinutesSeconds(hours, minutes, 0);
301 }
302
303 /**
304 * Obtains an instance of {@code ZoneOffset} using an offset in
305 * hours, minutes and seconds.
306 * <p>
307 * The sign of the hours, minutes and seconds components must match.
308 * Thus, if the hours is negative, the minutes and seconds must be negative or zero.
309 *
310 * @param hours the time-zone offset in hours, from -18 to +18
311 * @param minutes the time-zone offset in minutes, from 0 to ±59, sign matches hours and seconds
312 * @param seconds the time-zone offset in seconds, from 0 to ±59, sign matches hours and minutes
313 * @return the zone-offset, not null
314 * @throws DateTimeException if the offset is not in the required range
315 */
316 public static ZoneOffset ofHoursMinutesSeconds(int hours, int minutes, int seconds) {
317 validate(hours, minutes, seconds);
318 int totalSeconds = totalSeconds(hours, minutes, seconds);
319 return ofTotalSeconds(totalSeconds);
320 }
321
322 //-----------------------------------------------------------------------
323 /**
324 * Obtains an instance of {@code ZoneOffset} from a temporal object.
325 * <p>
326 * This obtains an offset based on the specified temporal.
327 * A {@code TemporalAccessor} represents an arbitrary set of date and time information,
328 * which this factory converts to an instance of {@code ZoneOffset}.
329 * <p>
330 * A {@code TemporalAccessor} represents some form of date and time information.
331 * This factory converts the arbitrary temporal object to an instance of {@code ZoneOffset}.
332 * <p>
333 * The conversion uses the {@link TemporalQueries#offset()} query, which relies
334 * on extracting the {@link ChronoField#OFFSET_SECONDS OFFSET_SECONDS} field.
335 * <p>
336 * This method matches the signature of the functional interface {@link TemporalQuery}
337 * allowing it to be used as a query via method reference, {@code ZoneOffset::from}.
338 *
339 * @param temporal the temporal object to convert, not null
340 * @return the zone-offset, not null
341 * @throws DateTimeException if unable to convert to an {@code ZoneOffset}
342 */
343 public static ZoneOffset from(TemporalAccessor temporal) {
344 Objects.requireNonNull(temporal, "temporal");
345 ZoneOffset offset = temporal.query(TemporalQueries.offset());
346 if (offset == null) {
347 throw new DateTimeException("Unable to obtain ZoneOffset from TemporalAccessor: " +
348 temporal + " of type " + temporal.getClass().getName());
349 }
350 return offset;
351 }
352
353 //-----------------------------------------------------------------------
354 /**
355 * Validates the offset fields.
356 *
357 * @param hours the time-zone offset in hours, from -18 to +18
358 * @param minutes the time-zone offset in minutes, from 0 to ±59
359 * @param seconds the time-zone offset in seconds, from 0 to ±59
360 * @throws DateTimeException if the offset is not in the required range
361 */
362 private static void validate(int hours, int minutes, int seconds) {
363 if (hours < -18 || hours > 18) {
364 throw new DateTimeException("Zone offset hours not in valid range: value " + hours +
365 " is not in the range -18 to 18");
366 }
367 if (hours > 0) {
368 if (minutes < 0 || seconds < 0) {
369 throw new DateTimeException("Zone offset minutes and seconds must be positive because hours is positive");
370 }
371 } else if (hours < 0) {
372 if (minutes > 0 || seconds > 0) {
373 throw new DateTimeException("Zone offset minutes and seconds must be negative because hours is negative");
374 }
375 } else if ((minutes > 0 && seconds < 0) || (minutes < 0 && seconds > 0)) {
376 throw new DateTimeException("Zone offset minutes and seconds must have the same sign");
377 }
378 if (minutes < -59 || minutes > 59) {
379 throw new DateTimeException("Zone offset minutes not in valid range: value " +
380 minutes + " is not in the range -59 to 59");
381 }
382 if (seconds < -59 || seconds > 59) {
383 throw new DateTimeException("Zone offset seconds not in valid range: value " +
384 seconds + " is not in the range -59 to 59");
385 }
386 if (Math.abs(hours) == 18 && (minutes | seconds) != 0) {
387 throw new DateTimeException("Zone offset not in valid range: -18:00 to +18:00");
388 }
389 }
390
391 /**
392 * Calculates the total offset in seconds.
393 *
394 * @param hours the time-zone offset in hours, from -18 to +18
395 * @param minutes the time-zone offset in minutes, from 0 to ±59, sign matches hours and seconds
396 * @param seconds the time-zone offset in seconds, from 0 to ±59, sign matches hours and minutes
397 * @return the total in seconds
398 */
399 private static int totalSeconds(int hours, int minutes, int seconds) {
400 return hours * SECONDS_PER_HOUR + minutes * SECONDS_PER_MINUTE + seconds;
401 }
402
403 //-----------------------------------------------------------------------
404 /**
405 * Obtains an instance of {@code ZoneOffset} specifying the total offset in seconds
406 * <p>
407 * The offset must be in the range {@code -18:00} to {@code +18:00}, which corresponds to -64800 to +64800.
408 *
409 * @param totalSeconds the total time-zone offset in seconds, from -64800 to +64800
410 * @return the ZoneOffset, not null
411 * @throws DateTimeException if the offset is not in the required range
412 */
413 public static ZoneOffset ofTotalSeconds(int totalSeconds) {
414 if (totalSeconds < -MAX_SECONDS || totalSeconds > MAX_SECONDS) {
415 throw new DateTimeException("Zone offset not in valid range: -18:00 to +18:00");
416 }
417 if (totalSeconds % (15 * SECONDS_PER_MINUTE) == 0) {
418 Integer totalSecs = totalSeconds;
419 ZoneOffset result = SECONDS_CACHE.get(totalSecs);
420 if (result == null) {
421 result = new ZoneOffset(totalSeconds);
422 SECONDS_CACHE.putIfAbsent(totalSecs, result);
423 result = SECONDS_CACHE.get(totalSecs);
424 ID_CACHE.putIfAbsent(result.getId(), result);
425 }
426 return result;
427 } else {
428 return new ZoneOffset(totalSeconds);
429 }
430 }
431
432 //-----------------------------------------------------------------------
433 /**
434 * Constructor.
435 *
436 * @param totalSeconds the total time-zone offset in seconds, from -64800 to +64800
437 */
438 private ZoneOffset(int totalSeconds) {
439 super();
440 this.totalSeconds = totalSeconds;
441 id = buildId(totalSeconds);
442 }
443
444 private static String buildId(int totalSeconds) {
445 if (totalSeconds == 0) {
446 return "Z";
447 } else {
448 int absTotalSeconds = Math.abs(totalSeconds);
449 StringBuilder buf = new StringBuilder();
450 int absHours = absTotalSeconds / SECONDS_PER_HOUR;
451 int absMinutes = (absTotalSeconds / SECONDS_PER_MINUTE) % MINUTES_PER_HOUR;
452 buf.append(totalSeconds < 0 ? "-" : "+")
453 .append(absHours < 10 ? "0" : "").append(absHours)
454 .append(absMinutes < 10 ? ":0" : ":").append(absMinutes);
455 int absSeconds = absTotalSeconds % SECONDS_PER_MINUTE;
456 if (absSeconds != 0) {
457 buf.append(absSeconds < 10 ? ":0" : ":").append(absSeconds);
458 }
459 return buf.toString();
460 }
461 }
462
463 //-----------------------------------------------------------------------
464 /**
465 * Gets the total zone offset in seconds.
466 * <p>
467 * This is the primary way to access the offset amount.
468 * It returns the total of the hours, minutes and seconds fields as a
469 * single offset that can be added to a time.
470 *
471 * @return the total zone offset amount in seconds
472 */
473 public int getTotalSeconds() {
474 return totalSeconds;
475 }
476
477 /**
478 * Gets the normalized zone offset ID.
479 * <p>
480 * The ID is minor variation to the standard ISO-8601 formatted string
481 * for the offset. There are three formats:
482 * <ul>
483 * <li>{@code Z} - for UTC (ISO-8601)
484 * <li>{@code +hh:mm} or {@code -hh:mm} - if the seconds are zero (ISO-8601)
485 * <li>{@code +hh:mm:ss} or {@code -hh:mm:ss} - if the seconds are non-zero (not ISO-8601)
486 * </ul>
487 *
488 * @return the zone offset ID, not null
489 */
490 @Override
491 public String getId() {
492 return id;
493 }
494
495 /**
496 * Gets the associated time-zone rules.
497 * <p>
498 * The rules will always return this offset when queried.
499 * The implementation class is immutable, thread-safe and serializable.
500 *
501 * @return the rules, not null
502 */
503 @Override
504 public ZoneRules getRules() {
505 return ZoneRules.of(this);
506 }
507
508 //-----------------------------------------------------------------------
509 /**
510 * Checks if the specified field is supported.
511 * <p>
512 * This checks if this offset can be queried for the specified field.
513 * If false, then calling the {@link #range(TemporalField) range} and
514 * {@link #get(TemporalField) get} methods will throw an exception.
515 * <p>
516 * If the field is a {@link ChronoField} then the query is implemented here.
517 * The {@code OFFSET_SECONDS} field returns true.
518 * All other {@code ChronoField} instances will return false.
519 * <p>
520 * If the field is not a {@code ChronoField}, then the result of this method
521 * is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)}
522 * passing {@code this} as the argument.
523 * Whether the field is supported is determined by the field.
524 *
525 * @param field the field to check, null returns false
526 * @return true if the field is supported on this offset, false if not
527 */
528 @Override
529 public boolean isSupported(TemporalField field) {
530 if (field instanceof ChronoField) {
531 return field == OFFSET_SECONDS;
532 }
533 return field != null && field.isSupportedBy(this);
534 }
535
536 /**
537 * Gets the range of valid values for the specified field.
538 * <p>
539 * The range object expresses the minimum and maximum valid values for a field.
540 * This offset is used to enhance the accuracy of the returned range.
541 * If it is not possible to return the range, because the field is not supported
542 * or for some other reason, an exception is thrown.
543 * <p>
544 * If the field is a {@link ChronoField} then the query is implemented here.
545 * The {@link #isSupported(TemporalField) supported fields} will return
546 * appropriate range instances.
547 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
548 * <p>
549 * If the field is not a {@code ChronoField}, then the result of this method
550 * is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)}
551 * passing {@code this} as the argument.
552 * Whether the range can be obtained is determined by the field.
553 *
554 * @param field the field to query the range for, not null
555 * @return the range of valid values for the field, not null
556 * @throws DateTimeException if the range for the field cannot be obtained
557 * @throws UnsupportedTemporalTypeException if the field is not supported
558 */
559 @Override // override for Javadoc
560 public ValueRange range(TemporalField field) {
561 return TemporalAccessor.super.range(field);
562 }
563
564 /**
565 * Gets the value of the specified field from this offset as an {@code int}.
566 * <p>
567 * This queries this offset for the value of the specified field.
568 * The returned value will always be within the valid range of values for the field.
569 * If it is not possible to return the value, because the field is not supported
570 * or for some other reason, an exception is thrown.
571 * <p>
572 * If the field is a {@link ChronoField} then the query is implemented here.
573 * The {@code OFFSET_SECONDS} field returns the value of the offset.
574 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
575 * <p>
576 * If the field is not a {@code ChronoField}, then the result of this method
577 * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
578 * passing {@code this} as the argument. Whether the value can be obtained,
579 * and what the value represents, is determined by the field.
580 *
581 * @param field the field to get, not null
582 * @return the value for the field
583 * @throws DateTimeException if a value for the field cannot be obtained or
584 * the value is outside the range of valid values for the field
585 * @throws UnsupportedTemporalTypeException if the field is not supported or
586 * the range of values exceeds an {@code int}
587 * @throws ArithmeticException if numeric overflow occurs
588 */
589 @Override // override for Javadoc and performance
590 public int get(TemporalField field) {
591 if (field == OFFSET_SECONDS) {
592 return totalSeconds;
593 } else if (field instanceof ChronoField) {
594 throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
595 }
596 return range(field).checkValidIntValue(getLong(field), field);
597 }
598
599 /**
600 * Gets the value of the specified field from this offset as a {@code long}.
601 * <p>
602 * This queries this offset for the value of the specified field.
603 * If it is not possible to return the value, because the field is not supported
604 * or for some other reason, an exception is thrown.
605 * <p>
606 * If the field is a {@link ChronoField} then the query is implemented here.
607 * The {@code OFFSET_SECONDS} field returns the value of the offset.
608 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
609 * <p>
610 * If the field is not a {@code ChronoField}, then the result of this method
611 * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
612 * passing {@code this} as the argument. Whether the value can be obtained,
613 * and what the value represents, is determined by the field.
614 *
615 * @param field the field to get, not null
616 * @return the value for the field
617 * @throws DateTimeException if a value for the field cannot be obtained
618 * @throws UnsupportedTemporalTypeException if the field is not supported
619 * @throws ArithmeticException if numeric overflow occurs
620 */
621 @Override
622 public long getLong(TemporalField field) {
623 if (field == OFFSET_SECONDS) {
624 return totalSeconds;
625 } else if (field instanceof ChronoField) {
626 throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
627 }
628 return field.getFrom(this);
629 }
630
631 //-----------------------------------------------------------------------
632 /**
633 * Queries this offset using the specified query.
634 * <p>
635 * This queries this offset using the specified query strategy object.
636 * The {@code TemporalQuery} object defines the logic to be used to
637 * obtain the result. Read the documentation of the query to understand
638 * what the result of this method will be.
639 * <p>
640 * The result of this method is obtained by invoking the
641 * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the
642 * specified query passing {@code this} as the argument.
643 *
644 * @param <R> the type of the result
645 * @param query the query to invoke, not null
646 * @return the query result, null may be returned (defined by the query)
647 * @throws DateTimeException if unable to query (defined by the query)
648 * @throws ArithmeticException if numeric overflow occurs (defined by the query)
649 */
650 @SuppressWarnings("unchecked")
651 @Override
652 public <R> R query(TemporalQuery<R> query) {
653 if (query == TemporalQueries.offset() || query == TemporalQueries.zone()) {
654 return (R) this;
655 }
656 return TemporalAccessor.super.query(query);
657 }
658
659 /**
660 * Adjusts the specified temporal object to have the same offset as this object.
661 * <p>
662 * This returns a temporal object of the same observable type as the input
663 * with the offset changed to be the same as this.
664 * <p>
665 * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}
666 * passing {@link ChronoField#OFFSET_SECONDS} as the field.
667 * <p>
668 * In most cases, it is clearer to reverse the calling pattern by using
669 * {@link Temporal#with(TemporalAdjuster)}:
670 * <pre>
671 * // these two lines are equivalent, but the second approach is recommended
672 * temporal = thisOffset.adjustInto(temporal);
673 * temporal = temporal.with(thisOffset);
674 * </pre>
675 * <p>
676 * This instance is immutable and unaffected by this method call.
677 *
678 * @param temporal the target object to be adjusted, not null
679 * @return the adjusted object, not null
680 * @throws DateTimeException if unable to make the adjustment
681 * @throws ArithmeticException if numeric overflow occurs
682 */
683 @Override
684 public Temporal adjustInto(Temporal temporal) {
685 return temporal.with(OFFSET_SECONDS, totalSeconds);
686 }
687
688 //-----------------------------------------------------------------------
689 /**
690 * Compares this offset to another offset in descending order.
691 * <p>
692 * The offsets are compared in the order that they occur for the same time
693 * of day around the world. Thus, an offset of {@code +10:00} comes before an
694 * offset of {@code +09:00} and so on down to {@code -18:00}.
695 * <p>
696 * The comparison is "consistent with equals", as defined by {@link Comparable}.
697 *
698 * @param other the other date to compare to, not null
699 * @return the comparator value, negative if less, positive if greater
700 * @throws NullPointerException if {@code other} is null
701 */
702 @Override
703 public int compareTo(ZoneOffset other) {
704 // abs(totalSeconds) <= MAX_SECONDS, so no overflow can happen here
705 return other.totalSeconds - totalSeconds;
706 }
707
708 //-----------------------------------------------------------------------
709 /**
710 * Checks if this offset is equal to another offset.
711 * <p>
712 * The comparison is based on the amount of the offset in seconds.
713 * This is equivalent to a comparison by ID.
714 *
715 * @param obj the object to check, null returns false
716 * @return true if this is equal to the other offset
717 */
718 @Override
719 public boolean equals(Object obj) {
720 if (this == obj) {
721 return true;
722 }
723 if (obj instanceof ZoneOffset) {
724 return totalSeconds == ((ZoneOffset) obj).totalSeconds;
725 }
726 return false;
727 }
728
729 /**
730 * A hash code for this offset.
731 *
732 * @return a suitable hash code
733 */
734 @Override
735 public int hashCode() {
736 return totalSeconds;
737 }
738
739 //-----------------------------------------------------------------------
740 /**
741 * Outputs this offset as a {@code String}, using the normalized ID.
742 *
743 * @return a string representation of this offset, not null
744 */
745 @Override
746 public String toString() {
747 return id;
748 }
749
750 // -----------------------------------------------------------------------
751 /**
752 * Writes the object using a
753 * <a href="{@docRoot}/serialized-form.html#java.time.Ser">dedicated serialized form</a>.
754 * @serialData
755 * <pre>
756 * out.writeByte(8); // identifies a ZoneOffset
757 * int offsetByte = totalSeconds % 900 == 0 ? totalSeconds / 900 : 127;
758 * out.writeByte(offsetByte);
759 * if (offsetByte == 127) {
760 * out.writeInt(totalSeconds);
761 * }
762 * </pre>
763 *
764 * @return the instance of {@code Ser}, not null
765 */
766 private Object writeReplace() {
767 return new Ser(Ser.ZONE_OFFSET_TYPE, this);
768 }
769
770 /**
771 * Defend against malicious streams.
772 *
773 * @param s the stream to read
774 * @throws InvalidObjectException always
775 */
776 private void readObject(ObjectInputStream s) throws InvalidObjectException {
777 throw new InvalidObjectException("Deserialization via serialization delegate");
778 }
779
780 @Override
781 void write(DataOutput out) throws IOException {
782 out.writeByte(Ser.ZONE_OFFSET_TYPE);
783 writeExternal(out);
784 }
785
786 void writeExternal(DataOutput out) throws IOException {
787 final int offsetSecs = totalSeconds;
788 int offsetByte = offsetSecs % 900 == 0 ? offsetSecs / 900 : 127; // compress to -72 to +72
789 out.writeByte(offsetByte);
790 if (offsetByte == 127) {
791 out.writeInt(offsetSecs);
792 }
793 }
794
795 static ZoneOffset readExternal(DataInput in) throws IOException {
796 int offsetByte = in.readByte();
797 return (offsetByte == 127 ? ZoneOffset.ofTotalSeconds(in.readInt()) : ZoneOffset.ofTotalSeconds(offsetByte * 900));
798 }
799
800 }